Often during the producing life of an oil well, it becomes desirable or necessary to produce from two or more different underground formations penetrated by the wellbore. This is commonly achieved through the use of packer assemblies containing two or more strings of conduit passing therethrough.
An example of such apparatus is shown in U.S. Pat. No. 2,965,173 in which a packer apparatus having dual conduit strings passing side-by-side therethrough has located on its outer surface resilient sealing cups having outwardly flared ends which are moved into sealing engagement by fluid pressure differentials above and below the cups.
Other types of multi-string packers include the inflatable or "bladder" type such as disclosed in U.S. Pat. No. 2,991,833 and the hydraulically actuated, compressible element, multi-string packer such as disclosed in U.S. Pat. No. 3,167,127. All known multi-string packers using mechanical anchors to lock the assembly to the casing wall utilize the wedge-type slip segments having teeth which are cammed or wedged into contact with the casing wall by the action of a wedging mandrel being forced inside the slip segments forcing them outwardly into contact with the casing. Other known types of slips include the hydraulic button type which are spring-retained radial pistons slidably located in the wall of the packer body and actuated outwardly against the spring retainer by hydraulic force applied from inside the packer assembly. An example of the button type slips is shown in U.S. Pat. No. 3,311,169.
The dual-string or dual-conduit packers normally are used with a standard single string packer located on the tubing string below the dual-packer, which tubing string communicates with a lower formation below the standard packer and is connected to one conduit in the dual packer and from there to a tubing string passing to the surface. The second formation is normally located between the standard packer and the dual packer and can be produced through the second conduit passing through the dual packer and communicating with a second tubing string extending to the surface.
The disadvantages of the prior art dual string packers are their complexity, extended length, and the tendency of the wedge-type slips to become disengaged by shifting or stretching of the tubing and/or casing during the production life of the packer.
Other types of multiple string packers include the hydraulically actuated packers such as those disclosed in U.S. Pat. Nos. 3,858,648; 3,851,707; and 3,851,705, all assigned to Dresser Industries, Inc., Dallas, Tex. These patents are directed to hydraulically actuated packers which may be undesirable in certain types of wells under certain conditions. In these circumstances only, a mechanically actuated packer is acceptable.
The disadvantages of the prior art devices are overcome by the present invention which comprises a highly versatile mechanically actuated packer for multi-string completions, which packer features an emergency tension shear that still allows the packer to be reset in the casing after an emergency shearing out.